Work on the 13.4ha depot site has so far focused on the massive foundations for 15 blocks of flats, five schools and a shopping centre to be built above the tracks. In all, contractor Gammon has to construct 820 cast insitu bored piles with diameters ranging from 1.2m to 2.8m through reclaimed marine muds and alluvium to bedrock.
Section 3 project manager Roger Bayliss describes the biggest piles as 'monstrous'. As well as having large diameters, 28 are longer than 75m and another 10 are more than 100m deep.
MTRC originally split the piling work into two contracts, but Gammon won both with a combined tender price of HK$591M. Before Christmas the site was a forest of cranes and piling rigs as the contractor headed for completion of 90% of the piles.
'We're on a tight programme, but we have a very experienced contractor, ' says MTRC's depot construction manager David Downs. 'They have been producing 100 piles a month consistently.'
At the peak of piling last year Gammon had around 50 piles on the go at any one time. This has slowed to around 30 as the contract nears completion. Intensity of the work and the size and depth of the piles prompted the contractor to set up its own batching plant on site to provide a steady, reliable supply of concrete.
Piling configurations were partly dictated by the depot's track layout. 'The first problem was sorting out the track alignments and finding space for the columns, ' says Ove Arup & Partners Hong Kong associate Peter Brotherton.
'We had to do a lot of work on the track alignments to get the columns in.'
In fact the columns are dual purpose.
As well as supporting the property development they will carry the suspended base slab for the depot. Although the depot is at grade, it will not rest directly on the reclaimed ground underneath. This is because settlement of as much as 2m is expected on the site over the depot's 120 year design life.
As piling nears completion, depot superstructure contractor Amec is preparing to move on to site and has already had initial partnering meetings with MTRC.
Eventually a Tseung Kwan O line station will be constructed alongside the depot although this will not be until around 2004, when the surrounding residential developments start to fill up.